Telephone-exchange trunk-circuit apparatus.



No. 772,871. Q PATENTED OCT. 18, 1904.

c. A. GRAPO. A v TELEPHONE EXCHANGE TRUNK 0111mm APPARATUS.

APPLICATION FILED B13129, 1902.

I N0 IAODEL.

UNITED STATES Patented October 18, 1904.

PATENT OFFICE.

ELECTRIC COMPANY, ILLINOIS.

OF CHICAGO, ILLINOIS, A CORPORATION OF TELEPHONE-EXCHANGE TRUNK-CIRCUIT APPARATUS.

SPECIFICATION forming part of Letters Patent No. 772,871, dated October 18, 1904:.

, Application filed December 29, 1902. Serial No 136,882. (No model.)

a full, clear, concise, and exact description.

My invention relates to trunk-line apparatus for telephone-exchanges.

' It is a well-recognized requirement in modern telephone-exchanges that most, if not all,

' work incidental to the supervision of the connection should be done by the answering operator, while the trunking operator should be required merely to put up the connection upon order from the answering operator and take it down upon signal,

My invention has for its object, in general, to provide an improved organization or systemin which an automatic ringing-key at the trunking-switchboard terminal of the line for signaling the called subscriber may be effectively controlled from the distant answeringswitchboard. m

More particularly my invention contemplates an arrangement whereby the ringingkey may be automatically actuated as a result of merely making connection with the trunkline'at both ends, and I further provide means whereby the answering operator may, if desired, resignal the called subscriber without requiring assistance from the trunking op- .erator.

I willdescribe my invention particularly by reference to the accompanying drawing, which is a diagram illustrating two subscribers lines extending from substations to different central ofiice's A B, with a trunk-line extending between the two oflices, with the connectionswitches and accessory apparatus for uniting the two lines through the trunk-line and transmittingthe incidental signals, the system being organized and equipped in accordance with my invention. I v

In the system illustrated the trunk-line ex tends in two metallic conductors 1 Qi'rom a springjack terminal a at the, answeringswitchboard A to a plug-terminal I) at the trunking-board B. A subscribers telephoneline is illustrated at each board provided with the usual spring-jack terminals 0 c, the substation apparatus of each line being of the usual type and including the usual gravity telephone-switch. At the switchboard each spring-jack is shown constructed with the usuallong and short line springs, connected,

respectively, with the line conductors of the telephone-line and a third contact or testring, as it is generally called, which forms the normally open terminal of a local switchboard-conductor 3, which extends to earth through the usual cut-oil relay (Z. The plugterminals of the operators cord-circuit at the answering-board and the plug-terminal of the trunk-line at the trunking-board are of the ,usual character adapted to cooperate with the spring-jacks of the type shown'that is to say, each plug has the usual tip, ring, and sleeve contacts which areadapted to register with the short and. long line springs and the test-ring, respectively, of. the .s pringjack, intowhich the plug may be inserted. The operators cord-circuit at the answering-board is of the usual type, which is well known in the art and which, being clearly illustrated by generally-accepted conventional symbols, does not require particular description. It will be noted that the grounded central battery 0 at the switchboard A is connected, as usual, in a bridge of the operators plug-circuit between the windings of the repeating-coil with the grounded pole of said battery toward the tip-strand of the cord-circuit, so that when the connecting-plug is inserted in the springjack a the grounded limb of the plug-circuit will be connected to the conductor 1 of the trunk-line. I

At the .trunking-switchboard B the trunkline is divided conductively by a repeatingcoil in accordance with the usual'practice, a battery 0' being connected in a bridge between the two windings of said repeating-coil, which are conductively in circuit with the extensions of line-wires l 2, leading to the tip and ring contacts, respectively, of plug 7). The pole of the battery which is connected to the tipstrand of the plug-circuitis grounded. 1 provide in association with the trunking operators plug-circuit at the board B an electromagnetic ringing-key f, which may have two switch-levers or armatures controlling the continuity of conductors 1 2 between the battery e and the plug. hen the magnet of the ringing-key is excited, it attracts its armatures and breaks the circuitot conductors 1 2, connecting the ends or terminals thereof leading to the plug with the poles of a generator G of ringing-current, whereby the bell at the station of the called line with which the plug may be connected is rung. in the system shown ringing-current will be applied as long as the magnetf remains excited. The magnet of the ringing-key f is included in a divided branch of a local circuit 6 3, which is primarily established in registering contacts of the connection-switch or the plug 6 and the spring-jack 0 of the called line and is further controlled by a relayg, which is responsive to a switch at the distant answering-board. 1 have shown the magnet of relay g at the board B included in a conductor 4., extending from the free pole of grounded battery (2 to the connection with the conductor 1 of the trunk-line leading to the switchboard A. It may here be remarked that for clearness of illustration 1 have shown two batteries, (each designated e;) but it isunderstood that these may be and preferably are one and the same central battery. In the system illustrated the ringing-key cannot be actuated until the trunk-plug is actually inserted in the springjack of the called line.

It has been common in systems heretofore to provide a conductor leading from the free pole of a battery, such as the battery 0, to the sleeve-contact of the trunk-plug to supply current to the cut-off relay of the line with which connection is made, a signal-lamp also being included in that portion of the circuit which is associated with the plug. In my system I may retain this conductor and the signal-lamp it therein and include the magnet of the ringing-key f in ashunt 5 around said signal-lamp. It has also been customary to 1 provide a relay 6 in the portion 6 of the local circuit which is established by the plug, this relay serving normally to connect the tip of the plug with the winding of the operators telephone induction-coil for the purpose of making the busy test, the induction-coil win ding being automatically cut off by the relay 2' when the magnet thereof is excited by the completion of the local circuit 6 3. In the system shown this relay is retained and is provided with an armature controlling a normally open break in the shunt-circuit 5 about the lamp 7L, said armature being also arranged to normally complete a path to ground from t said lamp-signal, which path is further controlled by a normally open cont-act of relay 1 In order that the ringing-current may be automatically cut oil when the called snbscriber answers, l control the application of ringing-current by means ot a magnet which is responsive to the teltaphone-switch at the called station. In the systen'l illustrated this oiiice is performed by the disconneet-magnet X, which is provided with a winding l" in the path of current from genea'ator (i to the called line, and a self-exciting winding t. \Vhen the magnet of relay Z' is excited, its switch-contacts are arranged to cut out the winding of the ringing-key magnet f and substitute in its place in circuit 5 the sellexeiting winding Zr 01'' the relay Z.

Normally the circuit conditions are as shown in the diagram. \Vhen the trunk operator at board B receives a call For a trunk connection, she may, in accordance with the usual practice, tell the answering operator over an order-wire which trunk to use in extending the connection. The A operator will then insert her calling-plug into the spring" jack (A of the trunk so designated, and as soon as she does so therelay will be excited by current from battery w in the branch l through the line conductor 1 of the trunk-line and thence to earth by way of the tip-strand of the operators cord-circuit at board A. The relay being excited will pull up its armature g whereupon the signal-lamp at the trunking-board will be lighted by current. passing from battery v through said lamp to earth by way of the armature 1 of relay and the normally closed contact of relay 1'. The trunking operator at the B switchboard being thus assured by the lighting o't lamp 1/. that the answering operator has plugged into the right trunk-linejack will insert the trunkplug Z into the spring-jack oi" the line wanted, having received the number of this line by orderwire from the answering o wrator. Having thus put up the connection, the work of the trunking operator is tinished until the connection is to be taken down again, since by means of my invention the bell at the substation of the line with which connection is made will be automatically rung until the c: lled party responds. The insertion ol the trunking-plug 7) into the spring-jack ot' a. line completes the local circuit (3 3. whereupon relay '1? is excited, as usual, and draws up its armatures, completing the slmnt-eircuit 5, which includes the winding f of the automatic ringing-key. Current from generator Ur is thus applied by said ringing-key through the winding Z." of the discomiect-relay t, to the called line. The winding Z", however, does not receive suflicient current to energize the relay until the called subscriber answers, because of the high resistance ot the signalbell at the substation. \Vhen the substationswitch is closed, however, increased current flows through the winding lc, whereby the relay is is excited and draws up its armature,

deenergized will reestablish the talking-circuit, so that conversation may be had over the trunk-line, and said ringing-key magnet will be permanently locked out irrespective of further changes in the electrical condition of the called line, but subject, however, to being reset from the answering-switch board. If it should be desired, for example, to send a recall-signal that is, to signal the called subscribera second time after he has once responded and then hung up his telephone suchsecond signal may be sent from the answering-switchboard without calling upon the trunking operator for assistance. The answering operator is provided with the usual supervisory signals, which informher of the condition of the connected lines, and if she wishes to send a second signal after the called party has hung up his telephone she may do so by simply withdrawing her calling-plug.

from the trunk-line spring-jack a, or in any other way breaking the circuit which energizes relay 9, and then reestablishing that circuit to again excite the relay. When the ref lay g becomes deenergized under the conditions above named, it will break the circuit of the locking-winding 77 whereby the disconnect-relay will be restored to its normal condition, in which the ringing-key magnet f is included in a local circuit in place of the locking-winding k When relay 9 again be,- comes energized, the ringing-key magnet f will therefore be again excited, as before eX- plained. v

It will be apparent that the invention herein set forth may be embodied in systems which may differ in many respects from that shown in the drawing, and the claims should be understood accordingly.

1. The combination with a telephone trunkline and connection-switches at each terminal for uniting the trunk-line with other lines, of an electromagnetic ringing-key for the trunkline at one end thereof, a local circuit for said ringing-key, and means controlled through the joint action of the connection-switches at both ends of the trunk-line for closing said local circuit, whereby the ringing-key is an tomatically actuated when connection is made at both ends of the trunk-line. I

2. The combination with atelephone trunkline extending from an answering-switchboard to a trunking-switchboard, and connectionswitches at each board for connecting the I trunk-line to other lines, of an electromagnetic ringing-key at the trunking-switchboard in a local circuit established through the agency of the corresponding connectionswitch, a relay g controlling said local circuit, and means for exciting said relay controlled through the agency of a switch at the answering-switchboard.

' 3. The combination with a calling'and a called telephone-line terminating on different switchboards, and a trunk-line extending between said switchboards, a source'of callingcurrent, an electrically-actuated key associated with the trunk-line and adapted when operated to apply calling-current to the called line, connection-switches at both ends ofthe trunk-line for uniting the trunk-line with the calling and called telephone-lines,'and means made operative by the closure of both said connection-switches for energizing the aforesaid electrically-actuated key.

4. The combination with a telephone trunkline extending from an answering-board to a trunking-board, and means at the trunkingboard for connecting the trunk-line with a subscribers line, of a source of calling-current, an electrically-actuated key controlling the application of said calling-current to the trunlcline, means made operative in completing connection with the trunk-line at both ends thereof to energize said calling-key, and electromagnetic mechanism controlled through the agency of 'the substation telephone-switch for deenergizing-said key to disconnect the source ofcalling-current from the line.

5. The combination with a telephone trunkline and connection-switches at each end for connecting the same to other lines, of an electromagnetic ringing-key at the trunking end, a trunk-line relay at the same end and means for exciting said relay controlled by a switch at the other end, a local circuitfor the said i connecting-relay, controlled by said trunkline relay.

6. The combination with a telephone trunkline extending from an answering-switchboard to a trunking board, a called subscribers line also terminating at the trunking-board, and a connection-switch for uniting the lines, of a source of calling-current and a key adapted to apply said current to the called line, a switch at the called substation, a magnet at the trunking-board responsive to said switch, mechanism controlled by said magnet for cutting off the source of calling-current, a locking-circuit for said magnet, a relay controlling the'flow of current through said locking-circuit, and a switch at the distant answering-board to which said relay is responsive; whereby the called station may be resignaled from. the an I sWering-switchboard.

7. The combination with a telephone trunkline and connection-switches at each end for connecting the trunk-line with other lines, of a source of calling-current at the trunking end of the trunk, an electromagnetic ringingkey for connecting said source of calling-current with the line, an actuating-circuit for said hey completed through the joint agency of the connection-switches at both ends of the trunk, a disconnecting device for denergizing said ringing-key to disconnect the source of calling-current from the line, said device being responsive to the electrical condition of the called line, and means controlled through the agency of the connection-switch at the other end of the trunk for reversing said disconnecting device, whereby callingcurrent may be reapplied to the called line.

8. The combination with a telephone trunkline extending from an answering to a trunl ing switchboard, of other lines terminating at each switchboard, a connection-switch at each end of the trunk-line for uniting it to the other lines, a source of calling-current at the trunking-board, an electromagnetic key controlling the connection of said source of calling-current with the called line, a trunkline relay associated with the trunk at the trunlvlng-board, an actuating-circuit for said relay controlled in the connection-switch at the answering-hoard, an actuating-circuit for said ringing-key controlled jointly by (he trunk-relay and the connection-switch at the trunking-board, a disconnect-relay for the ringing-key responsive to the electrical condition of the called line, said relay also controlling the actuating-circuit oi the ringingkey and operating to deprive the said key of current, a locking-circuit for said disconnectrelay completed in contacts of the same and CHARLES A. (ERA l( itnesscs:

HARRY A. Ruonns, N. 0. hence. 

